1. Field of the Invention
This invention relates to material handling systems and, more particularly, to an unmanned system for moving material within a structure having a plurality of vertically spaced levels, such as a hospital.
2. Description of the Prior Art
The efficient handling of material within structures not exclusively devoted to material storage, such as warehouses, has long been a problem to designers of material handling systems because the system must take into account primarily the nature of the activity being conducted within the structure. In other words, the material handling system must be designed around the activity rather than vice versa. The problem has become increasingly complex with the tendency toward construction of high-rise structures, which conserve expensive real estate, compared with the relative ease with which material can be handled in sprawling one-or two-story buildings.
A typical though not limiting example of complex material handling problems is that posed by a hospital with multiple floors. A prime concern in the design and organization of a hospital is to minimize the possible spread of germs or disease, which inherently are present, from one area to another. Yet enormous amounts of food, waste, and supplies and equipment (both clean and contaminated) must be moved within a hospital almost on a constant basis. In keeping with the principle of avoiding disease and germ proliferation, therefore, hospital planners have sought ways to move these materials without moving people with them because, of course, humans potentially represent major carriers of disease and germs. Another objective is to efficiently move such materials without comingling soiled materials with clean materials.
Typical of a material handling system designed for hospital use that minimizes human participation is the system shown in Beecher et al. U.S. Pat. No. 3,453,659. That system may use self-propelled electric vehicles of the type illustrated in Kohls U.S. Pat. No. 3,557,893 or Melke U.S. Pat. No. 4,044,853. These vehicles are adapted to be loaded with material to be moved throughout the hospital. Generally, the system involves the vertical movement of the driverless vehicles in elevators and rather long horizontal excursions of the vehicles on the hospital floors, the latter being accomplished by well-known vehicle guidance systems such as an embedded cable in the floor.
A major shortcoming of the system just discussed is the fact that the vehicles are powered by electric storage batteries. At the present time, such batteries are bulky, employ wet cells and require relatively long periods for recharging. Thus the use of wet storage batteries means labor expended in handling and recharging, potential danger with the chemicals present, and increased costs for maintaining a sufficient inventory of batteries to allow for out-of-service periods.
An alternative to the electric vehicle system for hospital use is a dumbwaiter system; examples of the latter are shown in Guilbert U.S. Pat. Nos. 3,432,055; 3,565,215; and 3,565,270. The dumbwaiter system employs an elevator or lift which contains the necessary mechanism to engage standard hospital carts queued in position outside the elevator doors and pull them into the elevator. Upon reaching the discharge floor, the mechanism within the elevator extends to place the carts at a predetermined position outside the elevator doors.
While the dumbwaiter system does minimize the vertical movement of attendants within the hospital, it has the drawbacks of allowing only restricted horizontal movement at the hospital floors and requiring that an elevator be dedicated to the system. Considering the expense of and limited space available for elevators in a multi-floor hospital, the latter drawback is serious.